Rozprawy doktorskie: „Transfer of oscillator strength”

1

Eustatiu, Iulia Gabriela. "Inner-shell electron energy loss spectroscopy and generalized oscillator strengths at high momentum transfer". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ66264.pdf.

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Holmes, Charlotte Emma. "Experimentally measured oscillator strengths and associated radiative lifetimes of neutral vanadium using Fourier Transform Spectroscopy and Laser-Induced Fluorescence". Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/34943.

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Modern astrophysical analysis requires increasing higher resolution laboratory spectra over a broader spectral range. The advances in ground- and space-based telescopes are highlighting the deficiencies in the current laboratory spectral database. This thesis reports on the research carried out on the high resolution laboratory measurements of the spectrum of neutral vanadium and the associated lifetime measurements to calculate transition probabilities. New measurements of radiative atomic lifetimes were made for 25 levels between 24648 cm-1 and 37518 cm-1 at the Lund Laser Center, Sweden, using the time resolved Laser-induced Fluorescence method. High Resolution Fourier Transform (FT) Spectroscopy is used to observe the hollow cathode lamp spectrum of neutral vanadium in the range 2000 cm-1 - 35000 cm-1. This range was covered using two high resolution FT Spectrometers in Imperial College London and Lund University (Sweden) with a resolving power of approximately 2 million and 1 million respectively. This resolving power enables line profiles to be fully resolved to the Doppler width. The high resolution spectra were used to measure the branching fractions of levels of interest which were then used in combination with the lifetime measurements to calculate the oscillator strengths. Across the UV, visible and IR spectral regions, radiative lifetimes and oscillator strengths for 208 lines between 3040 Å and 20000 Å from 39 upper energy levels are reported. 13 of these oscillator strengths have not been reported previously. Additionally new measurements were made of hyperfine structure splitting factors for 3 odd levels of V I lying between 24700 cm-1 and 28400 cm-1.

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3

Zhou, Yan. "Spin momentum transfer effects for spintronic device applications". Doctoral thesis, KTH, Materialfysik, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10605.

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The recent discovery that a spin-polarized current can exert a large torque on a ferromagnet, through direct transfer of spin angular momentum, offers the possibility of electrical current controlled manipulation of magnetic moment in nanoscale magnetic device structures. This so-called spin torque effect holds great promise for two applications, namely, spin torque oscillators (STOs) for wireless communication and radar communication, and spin transfer torque RAM (STT-RAM) for data/information storage. The STO is a nanosized spintronic device capable of microwave generation at frequencies in the 1-65 GHz range with high quality factors. Although the STO is very promising for future telecommunication, two major shortcomings have to be addressed before it can truly find practical use as a radio-frequency device. Firstly, its very limited output power has to be significantly improved. One possibility is the synchronization of two or more STOs to both increase the microwave power and further increase the signal quality. Synchronization of serially connected STOs has been suggested in this thesis. In this configuration, synchronization relies on phase locking between the STOs and their self-generated alternating current. While this locking mechanism is intrinsically quite weak, we find that the locking range of two serially connected spin-valve STOs can be enhanced by over two orders of magnitude by adjusting the circuit I-V phase to that of an intrinsic preferred phase shift between the STO and an alternating current. More recently, we have also studied the phase-locking of STOs based on magnetic tunnel junctions (MTJ-STO) to meet the power specifications of actual application where the rf output levels should be above 0 dBm (1 mW). In addition to the spin torque terms present in GMR spin valves, MTJs also exhibit a significant perpendicular spin torque component with a quite complex dependence on both material choices and applied junction bias. We find that the perpendicular torque component modifies the intrinsic preferred I-V phase shift in single MTJ-STOs in such a way that serially connected STOs synchronize much more readily without the need for additional circuitry to change the I-V phase. Secondly, equal attention has been focused on removing the applied magnetic field for STO operation, which requires bulky components and will limit the miniaturization of STO-based devices. Various attempts have been made to realize STOs operating in zero magnetic field. By using a tilted (oblique angle) polarizer (fixed layer) instead of an in-plane polarizer (standard STO), we show zero field operation over a very wide polarizer angle range without sacrificing output signal. In addition, the polarizer angle introduces an entirely new degree of freedom to any spin torque device and opens up for a wide range of additional phenomena. The STT-RAM has advantages over other types of memories including conventional MRAM in terms of power consumption, speed, and scalability. We use a set of simulation tools to carry out a systematic study on the subject of micromagnetic switching processes of a device for STT-RAM application. We find that the non-zero k spin wave modes play an important role in the experimentally measured switching phase boundary. These may result in telegraph transitions among different spin-wave states, and be related to the back-hopping phenomena where the switching probability will decrease with increasing bias in tunnel junctions.
QC 20100819

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Habouh, Mohamed I. "SHEAR TRANSFER STRENGTH OF CONCRETE PLACED AGAINST HARDENED CONCRETE". University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1439564977.

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Bonetti, Rodolfo Arturo. "Ultimate Strength of the Local Zone in Load Transfer Tests". Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/31392.

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An improved equation is presented for the prediction of the ultimate strength of the local zone in Load Transfer Tests. The derivation of this new formulation is the result of the investigation of the ultimate bearing strength of plain and reinforced concrete blocks, concentrically loaded. A total of 199 bearing tests were performed on plain and reinforced concrete prisms to evaluate the variables involved in the bearing problem. A finite element analysis of a typical square block loaded with different bearing areas was performed. Two equations, one for plain concrete and the other for reinforced concrete were derived using the Mohr failure criterion. The performance of the derived equations was evaluated against actual test data. The results of this evaluation showed very good agreement between the predicted ultimate strength and the actual test strength for both plain and reinforced concrete. For plain concrete specimens the ratio Ptest/Ppred was 1.05 with a coefficient of variation of 9 percent. In the case of reinforced concrete blocks the ratio Ptest/Ppred was 1.00 with a coefficient of variation of 14 percent.
Master of Science

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6

Razavi, Sabah. "Channel Estimation Error, Oscillator Stability And Wireless Power Transfer In Wireless Communication With Distributed Reception Networks". Digital WPI, 2019. https://digitalcommons.wpi.edu/etd-dissertations/508.

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This dissertation considers three related problems in distributed transmission and reception networks. Generally speaking, these types of networks have a transmit cluster with one or more transmit nodes and a receive cluster with one or more receive nodes. Nodes within a given cluster can communicate with each other using a wired or wireless local area network (LAN/WLAN). The overarching goal in this setting is typically to increase the efficiency of communication between the transmit and receive clusters through techniques such as distributed transmit beamforming, distributed reception, or other distributed versions of multi-input multi-output (MIMO) communication. More recently, the problem of wireless power transfer has also been considered in this setting. The first problem considered by this dissertation relates to distributed reception in a setting with a single transmit node and multiple receive nodes. Since exchanging lightly quantized versions of in-phase and quadrature samples results in high throughput requirements on the receive LAN/WLAN, previous work has considered an approach where nodes exchange hard decisions, along with channel magnitudes, to facilitate combining similar to an ideal receive beamformer. It has been shown that this approach leads to a small loss in SNR performance, with large reductions in required LAN/WLAN throughput. A shortcoming of this work, however, is that all of the prior work has assumed that each receive node has a perfect estimation of its channel to the transmitter. To address this shortcoming, the first part of this dissertation investigates the effect of channel estimation error on the SNR performance of distributed reception. Analytical expressions for these effects are obtained for two different modulation schemes, M-PSK and M2-QAM. The analysis shows the somewhat surprising result that channel estimation error causes the same amount of performance degradation in ideal beamforming and pseudo-beamforming systems despite the fact that the channel estimation errors manifests themselves quite differently in both systems. The second problem considered in this dissertation is related to oscillator stability and phase noise modeling. In distributed transmission systems with multiple transmitters in the transmit cluster, synchronization requirements are typically very strict, e.g., on the order of one picosecond, to maintain radio frequency phase alignment across transmitters. Therefore, being able to accurately model the behavior of the oscillators and their phase noise responses is of high importance. Previous approaches have typically relied on a two-state model, but this model is often not sufficiently rich to model low-cost oscillators. This dissertation develops a new three-state oscillator model and a method for estimating the parameters of this model from experimental data. Experimental results show that the proposed model provides up to 3 dB improvement in mean squared error (MSE) performance with respect to a two-state model. The last part of this work is dedicated to the problem of wireless power transfer in a setting with multiple nodes in the transmit cluster and multiple nodes in the receive cluster. The problem is to align the phases of the transmitters to achieve a certain power distribution across the nodes in the receive cluster. To find optimum transmit phases, we consider a iterative approach, similar to the prior work on one-bit feedback for distributed beamforming, in which each receive node sends a one-bit feedback to the transmit cluster indicating if the received power in that time slot for that node is increased. The transmitters then update their phases based on the feedback. What makes this problem particularly interesting is that, unlike the prior work on one-bit feedback for distributed beamforming, this is a multi-objective optimization problem where not every receive node can receive maximum power from the transmit array. Three different phase update decision rules, each based on the one-bit feedback signals, are analyzed. The effect of array sparsity is also investigated in this setting.

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Nassar, Adil J. "Investigation of Transfer Length, Development Length, Flexural Strength and Prestress Loss Trend in Fully Bonded High Strength Lightweight Prestressed Girders". Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/32941.

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Encouraged by the performance of high performance normal weight composite girders, Virginia Department of Transportation has sought to exploit the use of high strength lightweight composite concrete (HSLWC) girders to achieve economies brought about by the reduction of dead loads in bridges. Transfer Length measurements conducted on two AASHTO Type IV HSLWC prestressed girders, resulted in an average transfer length of 17 inches, well below the AASHTO and ACI guidance. Two girders composed of HSLWC AASHTO Type II girders and a 48" x 8" normal weight 4000-psi concrete deck were produced. The HSLWC Type II girders were cast of concretes with a compressive strength of 6380 psi and unit weight of 114 pcf. Full scale testing of the girders was conducted to evaluate development length and flexural strength in HSLWC composite girders. Embedment lengths of five, six and eight feet were evaluated. Tests indicated a development length of about 72 inches, marginally below the ACI and AASHTO stipulation. Four of eight strands in the girders showed general bond failure nevertheless, the tested girders exceeded their theoretical flexural capacity by 24 to 30 percent. A third composite girder was cast of a high strength normal weight concrete (HSNWC) Type II girder, and topped with a 48" x 8" normal weight 4000-psi concrete deck. This girder was intended as a control specimen to contrast its test results with the HSLWC composite girders. The targeted compressive strength of both the HSLWC and HSNWC AASHTO beams was 8000 psi. The compressive strength of the HSNWC mixture, however, was about 8990 psi compared to 6380 psi for the HSLWC mixture. Prestress losses in HSLWC AASHTO Type IV girders monitored over a nine-month period were found to be less than those calculated using the ACI and PCI models. Furthermore, the ACI model indicated that the effective prestressess retained in the HSLWC girders in 30 year's time are greater than 50% of the specified tensile strength of the strands.
Master of Science

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8

Tais, Senna. "Transfer Mechanisms of Eccentric Training : The effects of EMG-biofeedback in training". Thesis, Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:gih:diva-2303.

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Abstract Aim: The aim of this study was to investigate how neural mechanisms operate during maximum strength training in the Quadriceps Femoris muscle group. One of the main objectives is to investigate the effects of five weeks unilateral maximum eccentric strength training on contralateral neural adaptations. The second is to investigate the effects of adding electromyographic (EMG) biofeedback into the training intervention. Method: 20 healthy, recreationally active men and women had to undergo five weeks (three training sessions per week, resulting in 15 sessions in total) of maximum isokinetic unilateral eccentric strength training of the Quadriceps femoris muscle, with EMG biofeedback; FBG, n=10 five women and five men, or without EMG biofeedback; RTG n=10 five women and five men. The study was performed at the Laboratory of Biomechanics and Motor control, BMC Laboratory, Stockholm Sweden. Results: The results demonstrated an increase in concentric strength development in the trained leg; before 130 ± 43 Nm and after training 148 ± 46 Nm, (p=0.006). No significant increase in strength was detected for the untrained leg. Further, post hoc tests showed a tendency towards an increase in level of activation (LOA) of the trained leg in the FBG; from 69 ± 15 % before to 81 ± 13 % after training (p=0.097). No significant differences in the ecc:con EMG-ratio or in antagonist co-activation after the training intervention were shown. Conclusion: No significant difference in strength development was shown, whether training occurred with or without EMG biofeedback. However, eccentric training tended to induce transfer of neural activation to a maximum voluntary contraction (MVC) in the trained leg only in the group training with EMG biofeedback. In addition, the results revealed that eccentric strength training improved concentric strength in the trained leg but induced no transfer to the contralateral untrained leg. The benefits and prospects with incorporating feedback into training remains somewhat unknown and requires further research to obtain deeper understanding of the neural mechanisms affected by biofeedback.

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Rowe, Grant. "Adaptations underpinning the development, retention and loss of muscular strength in response to unilateral strength training and contralateral limb detraining". Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2020. https://ro.ecu.edu.au/theses/2335.

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Although adaptations to strength training should logically be confined to the trained muscles, a stimulus is also directed to the homologous, contralateral muscles that can improve strength of the contralateral limb even though it has not been exercised. This response is referred to as the cross-transfer effect or cross-education. There has been increasing research interest in the cross-transfer effect, and particularly its potential clinical use. However, several issues remain to be addressed with regards to its effectiveness in different populations. Pertinent to athletic and otherwise-active populations, no research has determined whether the cross-transfer effect occurs in previously-trained individuals. With recent research demonstrating that previously untrained individuals can prevent disuse-induce muscle loss in the contralateral limb by performing unilateral strength training, it is unclear whether the same outcome can be achieved in previously-trained participants. Understanding this response also has important implications for clinical practitioners who prescribe pre- or post-operative exercise programmes to patients. Therefore, the present research examined the cross-transfer effect in a homogenous group of previously-untrained participants after first completing 4 weeks of unilateral elbow flexion strength training of both arms (Study 2). This ensured that both limbs had a similar training status before phase two of the study and allowed for a detailed comparison to be made of adaptations to training in the force-dominant (stronger) versus force-non-dominant (weaker) arms. Subsequently, one group of subjects discontinued training completely while another group ceased training of only one arm (Study 3). This allowed an examination of whether strength loss occurs after a short period of strength training, and whether unilateral training could evoke a cross-transfer effect sufficient to attenuate the potential loss of strength in the non-training arm. To ensure that muscle size measurements could be accurately obtained in both exercise training phases, muscle size estimate errors following a single unilateral strength training session were determined on several consecutive days (Study 1). This information would provide clarity on the number of days the muscle should be rested before measurements were made. Although only peripheral quantitative computed tomography (pQCT) scanning was used to measure muscle size changes in Studies 2 and 3, ultrasonography was used in parallel in Study 1 to provide evidence as to whether the scanning techniques might be affected by common factors. Hence, the purposes of the present PhD research were threefold: (1) to investigate the muscle size estimate errors following a single unilateral strength training session using pQCT scanning and ultrasound imaging; 2) to quantify the adaptive responses in both the stronger and weaker elbow flexors to a short (4-week) period of unilateral strength training of both arms; and 3) to determine whether cross-transfer effects evoked by the continued training of one arm influence neuromuscular and strength changes in a contralateral limb that ceases training. In Study 1, pQCT- and ultrasound-derived estimates of muscle size increased markedly (5.4% and 6.9%, respectively) up to 72 h post-exercise and were significantly correlated. The similarity in change in these measures as well as the significant correlation between them indicates that changes measured by pQCT scanning reflect the same changes measured by ultrasound imaging. Also, as both measures of muscle size showed no signs of returning to baseline by 72 h post-exercise, muscle size measurements in the training studies (2 and 3) were conducted at least six days following the final training session. In Study 2, increases in 1-RM strength were observed in the stronger (+2.1 kg) and weaker (+1.8 kg) elbow flexors after 4 weeks of unilateral training of both arms, with no differences in strength or hypertrophic adaptations being detected between arms. Thus, pre-training between-limb asymmetries did not affect neuromuscular or strength adaptations to training, and between-limb strength differences were not reduced by the training; thus, reduction of between-limb differences might require different training stimuli to be applied to each arm. In Study 3, maximal isoinertial (1-RM) strength of the non-trained (weaker) arm increased statistically, although minimally (+0.8 kg), after continued training of the stronger, contralateral arm (+2.0 kg) while strength was maintained in both arms in the detraining group. Thus, cross-transfer effects were sufficient to improve contralateral limb strength in previously-trained muscles. These changes occurred despite a decrease in elbow flexor CSA (CSAFlexor) of 3.4% in the non-training arm, while continued training of the contralateral arm led to a further, 2.5%, increase in CSAFlexor. The findings provide evidence that cross-transfer effects allow for the retention of (or small improvement in) muscular strength in a previously-trained limb during a period of disuse, at least when the stronger arm is selected for continued training. The findings are consistent with recent data showing that disuse-induced strength loss can be prevented when untrained individuals are subjected to limb immobilisation. Nonetheless, as no strength loss was detected in either arm in the detraining group, the retention of strength in the non-trained arm of the training group may have also partly resulted from other causes. The improvement in contralateral limb strength without identification of any neuromuscular adaptations suggests that alterations in muscle activation patterns (i.e. rather than increased agonist activation per se) likely contributed to the observed changes. This series of studies provides valuable new information relating to the adaptations underpinning the development, retention, and loss of muscular strength in response to unilateral strength training and contralateral limb detraining.

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Chan, Phillip. "Jet impingement boiling heat transfer at low coiling temperatures". Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/401.

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The production of advanced high strength steels (AHSS) for use in the automotive and construction industries requires complex control of runout table (ROT) cooling. Advanced high strength steels require coiling at temperatures below 500 °C in order to produce a complex multi-phase microstructure. The research described here will investigate the boiling conditions that occur for moving plate experiments when steel is cooled towards low coiling temperatures. Experiments were performed on a pilot-scale ROT located at the University of British Columbia using industrially supplied steel plates. Tests were performed for four different speeds (0.3, 0.6, 1.0 and 1.3 m/s) and three different initial plate temperatures(350, 500 and 600 °C). Each plate was instrumented with thermocouples in order to record the thermal history of the plate. The results show that cooling is more effective at slower speeds within the stagnation zone for surface temperatures over 200 °C. Outside the stagnation zone regardless of speed cooling is primarily governed by air convection and radiation with minor effects from latent heat caused by splashing water. The maximum peak heat flux value increases with decreasing speed and occurs at a surface temperature of approximately 200 °C, regardless of speed. Below a surface temperature of 200 °C, speed has a negligible effect on peak heat flux. The maximum integrated heat flux seems to vary with speed according to a second order polynomial.

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Lee, Michael Medical Sciences Faculty of Medicine UNSW. "Neural mechanisms involved in cross-limb transfer of strength and ballistic motor learning". Publisher:University of New South Wales. Medical Sciences, 2008. http://handle.unsw.edu.au/1959.4/41279.

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The purpose of this thesis was to investigate the potential mechanisms and sites of neural adaptations that mediate cross-limb transfer of strength and motor learning that can occur subsequent to unilateral training. Better understanding of the mechanisms should allow therapeutic benefits of this effect to be assessed. There are two main classes of mechanisms that could contribute to cross-limb transfer. The first is described by the ??bilateral access?? hypothesis, which suggests that neural adaptations induced by training reside in bilaterally projecting motor areas that are accessible to the untrained (ipsilateral) hemisphere during task execution to facilitate performance. According to the alternative ??cross-activation?? hypothesis, activation of the untrained hemisphere during unilateral training leads to adaptations in the untrained hemisphere that cause improved performance with the opposite untrained limb. A series of studies were conducted in this research. We directly tested the cross-activation hypothesis via a reliable twitch interpolation technique involving transcranial magnetic stimulation (TMS). Four-weeks of strength training for the right wrist increased neural drive (from the untrained motor cortex) to the untrained left wrist. The data demonstrate that strength training of one limb can influence the efficacy of corticospinal pathways that project to the opposite untrained limb, consistent with the cross-activation hypothesis. To investigate the contribution of each hemisphere in cross-limb transfer, we applied repetitive TMS (rTMS) to the trained or the untrained motor cortex to disrupt brain processing after unilateral ballistic training. Learning to produce ballistic movements requires optimization of motor drive to the relevant muscles in a way that resembles high-force contractions performed during strength training. Ballistic skill transferred rapidly to the untrained hand and the improved performance was accompanied by bilateral increases in corticospinal excitability. Performance improvement in each hand was specifically suppressed by rTMS of the opposite hemisphere. Thus the motor cortex ipsilateral to the trained hand is critically altered during unilateral training; and neural adaptations within this untrained hemisphere are crucial in cross-limb transfer of ballistic skill. Overall, the data are in agreement with the cross-activation hypothesis for high-force and ballistic tasks, although they do not exclude the potential involvement of bilateral access mechanisms.

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Parlapalli, Rohit. "Effect of twist on load transfer and tensile strength in carbon nanotube bundles". University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1382372894.

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Wang, Rui. "Distributed Cooperative Communications and Wireless Power Transfer". Digital WPI, 2018. https://digitalcommons.wpi.edu/etd-dissertations/62.

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In telecommunications, distributed cooperative communications refer to techniques which allow different users in a wireless network to share or combine their information in order to increase diversity gain or power gain. Unlike conventional point-to-point communications maximizing the performance of the individual link, distributed cooperative communications enable multiple users to collaborate with each other to achieve an overall improvement in performance, e.g., improved range and data rates. The first part of this dissertation focuses the problem of jointly decoding binary messages from a single distant transmitter to a cooperative receive cluster. The outage probability of distributed reception with binary hard decision exchanges is compared with the outage probability of ideal receive beamforming with unquantized observation exchanges. Low- dimensional analysis and numerical results show, via two simple but surprisingly good approximations, that the outage probability performance of distributed reception with hard decision exchanges is well-predicted by the SNR of ideal receive beamforming after subtracting a hard decision penalty of slightly less than 2 dB. These results, developed in non-asymptotic regimes, are consistent with prior asymptotic results (for a large number of nodes and low per-node SNR) on hard decisions in binary communication systems. We next consider the problem of estimating and tracking channels in a distributed transmission system with multiple transmitters and multiple receivers. In order to track and predict the effective channel between each transmit node and each receive node to facilitate coherent transmission, a linear time-invariant state- space model is developed and is shown to be observable but nonstabilizable. To quantify the steady-state performance of a Kalman filter channel tracker, two methods are developed to efficiently compute the steady-state prediction covariance. An asymptotic analysis is also presented for the homogenous oscillator case for systems with a large number of transmit and receive nodes with closed-form results for all of the elements in the asymptotic prediction covariance as a function of the carrier frequency, oscillator parameters, and channel measurement period. Numeric results confirm the analysis and demonstrate the effect of the oscillator parameters on the ability of the distributed transmission system to achieve coherent transmission. In recent years, the development of efficient radio frequency (RF) radiation wireless power transfer (WPT) systems has become an active research area, motivated by the widespread use of low-power devices that can be charged wirelessly. In this dissertation, we next consider a time division multiple access scenario where a wireless access point transmits to a group of users which harvest the energy and then use this energy to transmit back to the access point. Past approaches have found the optimal time allocation to maximize sum throughput under the assumption that the users must use all of their harvested power in each block of the "harvest-then-transmit" protocol. This dissertation considers optimal time and energy allocation to maximize the sum throughput for the case when the nodes can save energy for later blocks. To maximize the sum throughput over a finite horizon, the initial optimization problem is separated into two sub-problems and finally can be formulated into a standard box- constrained optimization problem, which can be solved efficiently. A tight upper bound is derived by relaxing the energy harvesting causality. A disadvantage of RF-radiation based WPT is that path loss effects can significantly reduce the amount of power received by energy harvesting devices. To overcome this problem, recent investigations have considered the use of distributed transmit beamforming (DTB) in wireless communication systems where two or more individual transmit nodes pool their antenna resources to emulate a virtual antenna array. In order to take the advantages of the DTB in the WPT, in this dissertation, we study the optimization of the feedback rate to maximize the energy efficiency in the WPT system. Since periodic feedback improves the beamforming gain but requires the receivers to expend energy, there is a fundamental tradeoff between the feedback period and the efficiency of the WPT system. We develop a new model to combine WPT and DTB and explicitly account for independent oscillator dynamics and the cost of feedback energy from the receive nodes. We then formulate a "Normalized Weighted Mean Energy Harvesting Rate" (NWMEHR) maximization problem to select the feedback period to maximize the weighted averaged amount of net energy harvested by the receive nodes per unit of time as a function of the oscillator parameters. We develop an explicit method to numerically calculate the globally optimal feedback period.

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Meyer, Karl F. "Transfer and development length of 06-inch diameter prestressing strand in high strength lightweight concrete". Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/20727.

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Gregoire, Maxwell, Nathan Brooks, Raisa Trubko i Alexander Cronin. "Analysis of Polarizability Measurements Made with Atom Interferometry". MDPI AG, 2016. http://hdl.handle.net/10150/621408.

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We present revised measurements of the static electric dipole polarizabilities of K, Rb, and Cs based on atom interferometer experiments presented in [Phys. Rev. A 2015, 92, 052513] but now re-analyzed with new calibrations for the magnitude and geometry of the applied electric field gradient. The resulting polarizability values did not change, but the uncertainties were significantly reduced. Then, we interpret several measurements of alkali metal atomic polarizabilities in terms of atomic oscillator strengths f(ik), Einstein coefficients A(ik), state lifetimes tau(k), transition dipole matrix elements D-ik, line strengths S-ik, and van der Waals C-6 coefficients. Finally, we combine atom interferometer measurements of polarizabilities with independent measurements of lifetimes and C-6 values in order to quantify the residual contribution to polarizability due to all atomic transitions other than the principal ns-np(J) transitions for alkali metal atoms.

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Trent, Justin David. "Transfer Length, Development Length, Flexural Strength, and Prestress Loss Evaluation in Pretensioned Self-Consolidating Concrete Members". Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/33161.

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The first objective of this thesis was to determine the effect of using self-consolidating concrete versus normal concrete on transfer and development lengths, and flexural strengths of prestressed members. Three small rectangular members were made, two cast with SCC mixes and one cast with a conventional mix, to determine the transfer length of each mix. Transfer lengths of both ends of each member were determined by measuring the concrete surface strains. The change in the transfer length was monitored by determining the transfer length of each member at prestress release, 7 days after release, and 28 days after release. All concrete mixes had lower than code determined transfer lengths at prestress release. Each concrete mix showed between a 12 to 56 percent increase in transfer length after 28 days. One SCC mix exceeded the ACI code stipulated 50 strand diameters 7 days after prestress transfer. The other SCC mix was consistently below the transfer length of the conventional concrete.

Separate development length members were cast in a stay-in-place steel form used for creating structural double tees. Each development length member was a stub tee. Iterative load testing was performed to determine the development length of each SCC and conventional mix. Development lengths for both SCC mixes were approximately 20 percent shorter than ACI and AASHTO code predictions. A development length for the conventional concrete was not determined due to non-repeating test data. The flexural strength of each member was determined during load testing. All concrete mixes achieved higher than the ACI predicted strengths.

The second objective of this thesis was to experimentally measure prestress losses and compare these experimental values to theoretical models. Crack initiation and crack reopening tests were performed to experimentally determine the prestress losses in each member. Three theoretical models were evaluated, the sixth edition PCI Design Handbook suggested model, a 1975 PCI Committee on Prestress Losses model, and the AASHTO LRFD prestress loss model. The crack initiation experimental values tended to be between 10 and 15 percent lower than theoretical models. In general, the crack reopening prediction of the effective prestress had a good correlation with theoretical models. This suggests crack reopening tests can be used as predictors of effective prestress, and as such, predictors of prestress losses in future experimental research. Additionally, the concrete type was shown to affect the prestress losses determined in the development length members. The SCC members tended to have higher effective prestress forces than the conventional concrete members, and thus had less prestress losses due to creep and shrinkage than the conventional concrete members.
Master of Science

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Cross, Benjamin Thomas. "Structural Performance of High Strength Lightweight Concrete Pretensioned Bridge Girders". Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/26190.

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The use of high compressive strengths in prestressed bridge girders can lower costs by allowing for longer spans, increased girder spacing, and smaller cross-sections. If high strength lightweight concrete (HSLWC) is used, these advantages are further enhanced due to the corresponding reduction in self-weight. Additional benefits can then be realized in the form of more traffic lanes, increased load capacity, smaller substructures, reduced crane capacity requirements, and lower shipping costs. Despite the possible economic savings, HSLWC has been used infrequently in prestressed bridge girder applications across the nation. While recent research has been performed to extend the applicability of current bridge design specifications to normal weight concretes with strengths as high as 18 ksi, little has been done by comparison with regards to HSLWC. The purpose of the research in this report was to assess whether current bridge design specifications for transfer length, development length, prestress loss, camber, and flexural capacity are satisfactory for use with fully-bonded, pretensioned flexural members consisting of HSLWC and to make recommendations for improvements where necessary. Twelve high strength pretensioned beams of variable unit weight (eight lightweight beams and four normal weight beams) and strand size (eight beams with 0.5-in. strand and four beams with 0.6-in. strand) were cast at the Thomas M. Murray Structural Engineering Laboratory at Virginia Tech. These beams were allowed to sit for a period of several months after fabrication while measurements were taken regarding transfer length, prestress loss, and camber. After this period, the beams were load tested to collect development length data, flexural data, and further data related to prestress loss. In addition to the laboratory cast beams, prestress loss and camber data from six full-size bridge beams (five lightweight beams and one normal weight beam) cast as part of a separate project at Virginia Tech was examined. Analysis of the results for all beams shows that with a few caveats, the current AASHTO LRFD Specifications and other design methods examined regarding the topics under consideration are satisfactory for use in the design of HSLWC pretensioned bridge girders with properties similar to those of the beams studied.
Ph. D.

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18

Bi, Wu. "Racking Strength of Paperboard Based Sheathing Materials". Miami University / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=miami1091059928.

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Reutlinger, Christopher George. "Direct pull-out capacity and transfer length of 06-inch diameter prestressing strand in high-performance concrete". Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/19026.

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Heidarian, Negar. "A Homologous Study of Lifetimes and Oscillator Strengths of Ultraviolet Transitions in Singly Ionized Lead, Tin, and Germanium". University of Toledo / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1500466694480909.

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Nunes, Anne Catherine Lopes Pereira. "The impact of knowledge transfer on innovation in multinational corporations: exploring the contingent effects". Master's thesis, NSBE - UNL, 2009. http://hdl.handle.net/10362/9465.

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A Work Project, presented as part of the requirements for the Award of a Masters Degree in Management from the NOVA – School of Business and Economics
This direct research explores the contingencies of the relation between knowledge transfer and new product outcomes in Multinational companies. Indeed, in a MNC context, “the conditions under which such knowledge transfer can serve to induce positive outcomes remain unclear.”(Lee, 2008, p 1) After a deep literature review of knowledge transfer and new product outcomes literature, an exploratory study was conducted to understand which factors can influence the impact of knowledge transfer in new product outcomes, with the purpose to give insights about the way to approach a further study. We propose the following three internal contingencies: network strength, absorptive capacity, customer orientation and an external one: technological turbulence, through a semi structured interview guide conducted with 12 top managers. Globally, the exploratory study has provided confirmation for the variables proposed.

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Al, Mahmud Shamsul Arefeen. "Wireless Power Transfer : Machine Learning Assisted Characteristics Prediction for Effective Wireless Power Transfer Systems". Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-286673.

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One of the main challenges in wireless power transfer (WPT) devices is performance degradation when the receiver’s position and characteristics vary. The variations in the system parameters such as load impedance and coupling strength in WPT devices affect performance characteristics such as output voltage and power. When the system parameters are different from the optimal operating conditions, the performances are degraded. Therefore, the load impedance and coupling strength must be monitored to do the necessary optimization and control. However, such control approaches require additional sensing circuits and a data communication link between transmitter- and receiver-sides. This study proposes a new machine learning (ML) assisted WPT system that predicts the power delivered to the receiver by only using measurements at the transmitter-side. In addition, a method is also proposed to estimate load impedance and coupling coefficient using machine learning approach. We study what parameters measurable at the transmitter-side can be used to predict the output power delivered to receivers at variable load impedance and coupling strengths. In the proposed method, the output power of an inductor-capacitor-capacitor (LCC)-Series tuned WPT system is successfully predicted only using the measured root-mean-square (RMS) of the input current. Random forest algorithm has shown best accuracy to estimate the output power based on transmitter-side parameters only. The proposed approach is experimentally validated using a laboratory prototype. Harmonic components of the input current are used to assess the load impedance and coupling coefficient successfully. Multi-output regression has the highest accuracy for estimating the load impedance and coupling coefficient. The proposed ML algorithm is also used to classify the turn-on and -off regimes to ensure high-efficient operation.
En av de viktigaste utmaningarna med trådlösa kraftöverföring enheter är degraderingen av prestandan när mottagarens position och egenskaper varierar. Variationerna av systemets parametrar, såsom belastningsmotstånd och kopplings styrka i WPT-anordning, påverkar prestanda egenskaperna såsom spänning och effekt. När system parametrarna skiljer sig från de optimala drifts förhållandena, försämras prestandan. Därför måste luftmotståndet och kopplings styrkan övervakas, för att göra nödvändig optimering och kontroll. Sådana styrmetoder kräver emellertid ytterligare avkännings kretsar, och en data kommunikationslänk mellan sändar- och mottagarsidan. Denna studie föreslår ett nytt maskininlärning assisterat WPT-system, som förutsäger kraften som levereras till mottagaren genom att endast använda mätningar på sändarsidan. Dessutom föreslås en metod för att detektera belastningsimpedans och kopplings koefficient med användning av maskin inlärningsmetoder. Vi studerar vilka parametrar som är mätbara på sändarsidan och som kan användas för att förutsäga utgången effekten som levereras till mottagare vid varierande belastningsmotstånd och kopplings nivåer. I den föreslagna metoden förutses framgångs effekten för ett induktor-kondensator-kondensator LCCserie avstämt WPT-system endast framgångsrikt med hjälp av det uppmätta effektivvärdet för ingångs strömmen. Slumpmässig skogsalgoritm har visat exceptionell noggrannhet för att uppskatta uteffekten endast baserat på sändarsidans parametrar. Den föreslagna metoden valideras experimentellt med användning av en laboratorium prototyp. Harmoniska komponenter i ingångs strömmen används för att framgångsrikt bedöma last motståndet och kopplings koefficienten. Multi-utgångsregression har verkat vara mycket exakt för att uppskatta belastningsimpedans och kopplingskoefficient. Den föreslagna maskininlärning algoritmen används också för att klassificera start-och-off-regimer för att säkerställa hög effektiv drift.

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Wiggam, Marilyn K. "Predicting adult learner academic persistence: Strength of relationship between age, gender, ethnicity, financial aid, transfer credits, and delivery methods". The Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=osu1092748628.

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Ishihara, Hiroyuki. "Dynamics of reverse knowledge transfer in MNCs : case studies of an American MNC and its Japanese subsidiary". Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/dynamics-of-reverse-knowledge-transfer-in-mncs-case-studies-of-an-american-mnc-and-its-japanese-subsidiary(fd5baaad-b671-4daa-9885-96d5db08028b).html.

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Recently, facing the fierce competition around the world, the headquarters of many MNCs are under pressure to make a decision quickly and effectively for their global marketing strategy. Under such a situation, how effectively the headquarters can obtain knowledge regarding the market situation of subsidiaries around the world is important. In this research, the concept of reverse knowledge transfer is applied to the space of the headquarters' acquisition of knowledge from subsidiaries, from the perspective of decision-making for global marketing strategies. In the extant literature, however, studies on reverse knowledge transfer analyzing the mechanisms dynamically in a multi-faceted way from the perspective of transferring marketing-related knowledge are rare. In order to capture the reverse knowledge transfer mechanisms in a MNC precisely and dynamically, three case studies of the headquarters of an American MNC and its Japanese subsidiary were conducted. Through analysis of the case studies, two new factors were found; one is 'bypass effect', and the other is 'heeding capacity'. By bringing in those new factors, a new dynamic model for reverse knowledge transfer is proposed.

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Venkataraman, Manoj. "THE EFFECT OF COLLOIDAL STABILITY ON THE HEAT TRANSFER CHARACTERISTICS OF NANOSILICA DISPERSED FLUIDS". Master's thesis, University of Central Florida, 2005. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3656.

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Addition of nano particles to cooling fluids has shown marked improvement in the heat transfer capabilities. Nanofluids, liquids that contain dispersed nanoparticles, are an emerging class of fluids that have great potential in many applications. There is a need to understand the fundamental behavior of nano dispersed particles with respect to their agglomeration characteristics and how it relates to the heat transfer capability. Such an understanding is important for the development and commercialization of nanofluids. In this work, the stability of nano particles was studied by measuring the zeta potential of colloidal particles, particle concentration and size. Two different sizes of silica nano particles, 10 nm and 20 nm are used in this investigation at 0.2 vol. % and 0.5 vol. % concentrations. The measurements were made in deionized (DI) water, buffer solutions at various pH, DI water plus HCl acid solution (acidic pH) and DI water plus NaOH solution (basic pH). The stability or instability of silica dispersions in these solutions was related to the zeta potential of colloidal particles and confirmed by particle sizing measurements and independently by TEM observations. Low zeta potentials resulted in agglomeration as expected and the measured particle size was greater. The heat transfer characteristics of stable or unstable silica dispersions using the above solutions were experimentally determined by measuring heat flux as a function of temperature differential between a nichrome wire and the surrounding fluid. These experiments allowed the determination of the critical heat flux (CHF), which was then related to the dispersion characteristics of the nanosilica in various fluids described above. The thickness of the diffuse layer on nano particles was computed and experimentally confirmed in selected conditions for which there was no agglomeration. As the thickness of the diffuse layer decreased due to the increase in salt content or the ionic content, the electrostatic force of repulsion cease to exist and Van der Waal's force of agglomeration prevailed causing the particles to agglomerate affecting the CHF. The 10nm size silica particle dispersions showed better heat transfer characteristics compared to 20nm dispersion. It was also observed that at low zeta potential values, where agglomeration prevailed in the dispersion, the silica nano particles had a tendency to deposit on the nickel chromium wire used in CHF experiments. The thickness of the deposition was measured and the results show that with a very high deposition, CHF is enhanced due to the porosity on the wire. The 10nm size silica particles show higher CHF compared to 20nm silica particles. In addition, for both 10nm and 20nm silica particles, 0.5 vol. % concentration yielded higher heat transfer compared to 0.2 vol. % concentration. It is believed that although CHF is significantly increased with nano silica containing fluids compared to pure fluids, formation of particle clusters in unstable slurries will lead to detrimental long time performance, compared to that with stable silica dispersions.
M.S.M.S.E.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Materials Science and Engineering

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Heard, William Franklin. "Diagonal and horizontal stiffeners for shear transfer in rigid frame square knees". Master's thesis, Mississippi State : Mississippi State University, 2006. http://library.msstate.edu/etd/show.asp?etd=etd-11092006-214442.

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Derakhti, Mikael, i John Åkerlund. "Cross Education; : The effect of 10 weeks of unilateral resistance training on strength and hypertrophy". Thesis, Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:gih:diva-4475.

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Abstract Aim The main purpose of this study was to investigate Cross Education (CE), and how gender, detraining and leg dominance affects CE in previously untrained subjects when conducting a unilateral resistance training program. We also investigated if unilateral resistance training can give a hypertrophic response. Method Twenty healthy previously untrained individuals, 10 females and 10 males, were recruited as volunteer participants. The participants were randomly assigned to train either left or right leg. The training intervention was 10 weeks (34 sessions) of unilateral resistance training in the leg press and leg extension, sixteen of the participants fulfilled the criteria for inclusion. After two initial familiarization the participants trained conventional resistance training three times a week (week 1-3, 5-7 and 9-10) and Blood Flow Restriction Training (BFRT) five times a week (week 4 and 8). One repetition maximum for both legs in the leg press and leg extension was tested pre-, post and post20 to the training intervention as well as ultrasound measurements of muscle thickness. Results The ten-week training period resulted in a significant increase of maximal strength for the untrained leg 18,9 %, (16,6) (p < 0,01) in the leg press and 6,7 %, (3,7) (p < 0,05) in the leg extension. When comparisons between gender were made only men had a significant increase 26,5 %, (16,7) (p < 0,01) in the leg press and 9,9 %, (4,7) (p < 0,05) in the leg extension. Also, we saw a significant difference between women and men on a group level. Comparisons of dominant vs non-dominant leg showed that training the dominant leg resulted in a significant increase of maximal strength in the untrained leg in both the leg press 22 %, (17,9) (p < 0,01) and leg extension 10,1 %, (4,3) (p < 0,05). The maximal strength in the untrained leg was not significantly altered by the detraining period and a significant increase of muscle thickness could be seen in the untrained leg at MP50 4,7 %, (1,3) (p < 0,01). Conclusion The conclusions are that a ten week unilateral resistance training intervention results in a CE effect for men but not for women and that this type of training also can result in an increased muscle thickness in the untrained leg. Our findings also supports that training the dominant limb has superior effect on achieving a CE effect. Lastly we conclude that a twenty week detraining period did not affect the CE achieved strength.
Abstrakt Syfte Studiens huvudsakliga syfte var att undersöka Cross Education (CE) och hur kön, viloperiod och ben-dominans påverkar CE hos otränade individer när man undergår ett unilateralt styrketräningsprogram. Vi undersökte även om ett unilateral styrketräning kunde ge ett hypertrofisvar. Metod Tjugo friska otränade och för närvarande inaktiva individer, tio kvinnor och tio män rekryterades som frivilliga deltagare. Deltagarna randomiserades för att träna antingen vänster eller höger ben. Träningsperioden var tio veckor (trettiofyra pass) av unilateral styrketräning i benpress och benspark, sexton deltagare uppfyllde kriterierna för inkludering. Två initiala familjäriseringspass hölls varefter träningen delades in i två typer av träning, dels konventionell styrketräning tre gånger i veckan (vecka 1-3, 5-7 och 9-10) och dels Blood Flow Restriction Training (BFRT) fem gånger i veckan (vecka 4 och 8). Före, efter och efter tjugo veckor testades one repetition maximum för båda benen i benpress och benspark samt att ultraljudsmätningar för muskeltjocklek utfördes. Resultat Den tio veckor långa träningsperioden resulterade i en signifikant ökning av den maximala styrkan för det otränade benet 18,9 % (16,6) (p < 0,010) i benpressen och 6,7 % (3,7) (p < 0,050) i bensparken. När jämförelser gjordes mellan könen så hade enbart män en signifikant ökning, 26,5 % (16,7) (p < 0,010) i benpressen och 9,9 % (4,7) (p < 0,050) i bensparken. Vi fann även att det var en signifikant skillnad mellan kvinnor och män på gruppnivå. Jämförelser mellan dominant och icke-dominant ben visade att träning av det dominanta benet resulterade i en signifikant styrkeökning i både benpress 22 % (17,9) (p < 0,010) och benspark 10,1 % (4,3) (p < 0,050). Den maximala styrkan i det otränade benet påverkades inte signifikant av en viloperiod och en signifikant ökning i muskeltjocklek kunde ses i det otränade benet i MP50 4,7 % (1,3) (p < 0,010) Konklusion Slutsatserna är att en tio veckors unilateral styrketräningsintervention resulterar i en CE effekt hos män men inte hos kvinnor, och att denna typ av träning kan resultera i en ökad muskeltjocklek i det otränade benet. Våra fynd styrker att träning av den dominanta lemmen har större effekt på CE. Slutligen drar vi slutsatsen att en tjugo veckors viloperiod inte påverkar CE-styrkan.

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Fiore, Vincenzo. "Fully integrated systems with on-chip galvanic isolation in silicon technology". Doctoral thesis, Università di Catania, 2015. http://hdl.handle.net/10761/3866.

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In this work the investigation on fully integrated systems providing on-chip galvanic isolation is presented, which exploits a silicon technology by STMicroelectronics. This research is mainly motivated by the higher level of integration that is demanded to the next generation of power converters and general applications featuring galvanic isolation. State-of the art implementations rely on complex post-processed passive devices to implement isolated power transfer within multi-die system in packages. In this work, two silicon implementations are mainly discussed, i.e. a step-up power transfer system and the ASK data receivers of a data/power transfer system. They achieve up to 980 mW output power with 29.6% efficiency and up to 40 Mbps with 5% modulation index, respectively, thus showing enhanced performance with respect to the state-of-the-art. Each system requires only two silicon chips to implement both galvanic isolation and power transfer, thus achieving the highest possible level of integration for a pure silicon technology.

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Gilmore, Kevin R. "Treatment of High-Strength Nitrogen Wasetewater With a Hollow-Fiber Membrane-Aerated Biofilm Reactor: A Comprehensive Evaluation". Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/28711.

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Protecting the quality and quantity of our water resources requires advanced treatment technologies capable of removing nutrients from wastewater. This research work investigated the capability of one such technology, a hollow-fiber membrane-aerated biofilm reactor (HFMBR), to achieve completely autotrophic nitrogen removal from a wastewater with high nitrogen content. Because the extent of oxygenation is a key parameter for controlling the metabolic processes that occur in a wastewater treatment system, the first part of the research investigated oxygen transfer characteristics of the HFMBR in clean water conditions and with actively growing biofilm. A mechanistic model for oxygen concentration and flux as a function of length along the non-porous membrane fibers that comprise the HFMBR was developed based on material properties and physical dimensions. This model reflects the diffusion mechanism of non-porous membranes; namely that oxygen follows a sorption-dissolution-diffusion mechanism. This is in contrast to microporous membranes in which oxygen is in the gas phase in the fiber pores up to the membrane surface, resulting in higher biofilm pore liquid dissolved oxygen concentrations. Compared to offgas oxygen analysis from the HFMBR while in operation with biofilm growing, the model overpredicted mass transfer by a factor of approximately 1.3. This was in contrast to empirical mass transfer coefficient-based methods, which were determined using either bulk aqueous phase dissolved oxygen (DO) concentration or the DO concentration at the membrane-liquid interface, measured with oxygen microsensors. The mass transfer coefficient determined with the DO measured at the interface was the best predictor of actual oxygen transfer under biofilm conditions, while the bulk liquid coefficient underpredicted by a factor of 3. The mechanistic model exhibited sensitivity to parameters such as the initial lumen oxygen concentration (at the entry to the fiber) and the diffusion coefficient and partitioning coefficients of oxygen in the silicone membrane material. The mechanistic model has several advantages over empirical-based methods. Namely, it does not require experimental determination of KL, it is relatively simple to solve without the use of advanced mathematical software, and it is based upon selection of the membrane-biofilm interfacial DO concentration. The last of these is of particular importance when designing and operating HFMBR systems with redox (aerobic/anoxic/anaerobic) stratification, because the DO concentration will determine the nature of the microenvironments, the microorganisms present, and the metabolisms that occur. During the second phase of the research, the coupling of two autotrophic metabolisms, partial nitrification to nitrite (nitritation) and anaerobic ammonium oxidation, was demonstrated in a single HFMBR. The system successfully treated a high-strength nitrogen wastewater intended to mimic a urine stream from such sources as extended space missions. For the last 250 days of operation, operating with an average oxygen to ammonia flux (JO2/JNH4+) of 3.0 resulted in an average nitrogen removal of 74%, with no external organic carbon added. Control of nitrite-oxidizing bacteria (NOB) presented a challenge that was addressed by maintaining the JO2/JNH4+ below the stoichiometric threshold for complete nitrification to nitrate (4.57 g O2 / g NH4 +). The DO-limiting condition resulted in formation of harmful gaseous emissions of nitrogen oxides (NO, N2O), which could not be prevented by short-term control strategies. Controlling JO2/JNH4+ prevented NOB proliferation long enough to allow an anaerobic ammoniaoxidizing bacteria (AnaerAOB) population to develop and be retained for >250 days. Addition of a supplemental nutrient solution may have contributed to the growth of AnaerAOB by overcoming a possible micronutrient deficiency. Disappearance of the gaseous nitrogen oxide emissions coincided with the onset of anaerobic ammonium oxidation, demonstrating a benefit of coupling these two autotrophic metabolisms in one reactor. Obvious differences in biofilm density were evident across the biofilm depth, with a region of low density in the middle of the biofilm, suggesting that low cell density or exocellular polymeric substances were primarily present in this region, Microbial community analysis using fluorescence in situ hybridization (FISH) did not reveal consistent trends with respect to length along the fibers, but radial stratification of aerobic ammonia-oxidizing bacteria (AerAOB), NOB, and AnaerAOB were visible in biofilm section samples. AerAOB were largely found in the first 25% of the biofilm near the membrane, AnaerAOB were found in the outer 30%, and NOB were found most often in the mid-depth region of the biofilm. This community structure demonstrates the importance of oxygen availability as a determinant of how microbial groups spatially distribute within an HFMBR biofilm. The combination of these two aspects of the research, predictive oxygen transfer capability and the effect of oxygen control on performance and populations, provides a foundation for future application of HFMBR technology to a broad range of wastewaters and treatment scenarios.
Ph. D.

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Carroll, James Christopher. "Grade 300 Prestressing Strand and the Effect of Vertical Casting Position". Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/28806.

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The purpose of this study was to investigate the influence an increase in strand strength and the effect the as-cast vertical location had on transfer length, development length, and flexural strength and to resolve the discrepancies regarding the definition of the top-bar/strand effect. Two types of test specimens were fabricated and tested investigating each respective item. The increase in strand strength was found to influence transfer length, development length, and flexural strength, while the as-cast vertical location was only found to influence transfer length, and in turn development length. Contrary to the historical definition, the top-bar/strand effect was found to be more dependent on the amount of concrete cast above the strand than the amount below it, with transfer lengths showing a steady increase with a decrease in the amount of concrete cast above the strand. As a result of the findings of this study, a new transfer length equation was proposed and a previously proposed flexural bond length equation was recommended for use in lieu of the current code provisions. The current equations for flexural strength were found to give adequate estimates for flexural strength, although a decrease in ductility was noted.
Ph. D.

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31

Quinsat, Michaël. "Etude d'un auto-oscillateur non-isochrone : Application à la dynamique non-linéaire de l'aimantation induite par transfert de spin". Thesis, Grenoble, 2012. http://www.theses.fr/2012GRENY083/document.

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Les oscillateurs à transfert de spin (STO) sont des oscillateurs Radiofréquence nanométriques dont la fréquence peut être variée d'un ordre de grandeur. Cette forte agilité en fréquence provient des propriétés non-linéaires de la dynamique de l'aimantation induite par le transfert de spin (STT) dans des multicouches magnétiques nano-structurées. Cette forte agilité en fréquence a le désavantage d'induire une forte sensibilité au bruit. La pureté spectrale des STO est alors bien en dessous des pré-requis pour les applications en télécommunications. Les principales propriétés de la dynamique de l'aimantation induite par le STT ont été décrites simplement à l'aide de la théorie non-linéaire des ondes de spin. Cependant des informations importantes sur le mode d'excitation sont enfouies dans des paramètres phénoménologiques tels que le couplage amplitude-phase NU et le taux de relaxation Gp. La détermination de ces paramètres avec précision est d'un intérêt primordial pour la description de la dynamique non-linéaire. Cette thèse décrit plusieurs méthodes expérimentales pour extraire ces paramètres. La première est la spectroscopie de bruit depuis le domaine temporel qui permet l'extraction des Densités Spectrales de Puissance du bruit d'amplitude et de phase. Leur analyse dans le cadre des modèles théoriques permet non seulement d'extraire directement les paramètres non-linaires mais également de quantifier le bruit de phase qui a un intérêt technologique. Ceci est démontré pour des dispositifs basés sur des jonctions tunnels magnétiques. La deuxième méthode est basée sur l'analyse des largeurs de raies des harmoniques du signal, où il est montré que du fait des propriétés non-isochrones des STO, la relation entre Dfn et Df1 est non triviale et permet l'extraction de NU et Gp. Nous utilisons alors toutes les informations obtenues sur le régime autonome de la dynamique des STO pour comprendre leur dynamique non-autonome qui sont des pré-requis à leurs utilisations dans des architectures RF complexes
Spin Torque Oscillators (STO) are nano-sized Radio-Frequency oscillators whose frequency agility can be tuned by an order of magnitude. This tuning originates from the non-linear properties of the underlying magnetization dynamics that is induced by spin transfer torque (STT) in multilayered magnetic nanostructures. Being highly tunable in frequency has the inconvenient of creating a very strong sensitivity to noise. As a result the spectral purity of STOs is far below the one required for applications for instance in telecommunications. The magnetization dynamics induced by STT has been described theoretically in the frame of nonlinear spin wave theory that makes the essential features of the underlying properties very transparent. However important information on the excitation mode are "buried" in phenomenological parameters such as NU the amplitude-phase coupling and Gp the amplitude relaxation rate. Determining these parameters with accuracy from experiments is thus an important issue. This thesis describes several experimental methods to extract these parameters. The first is time domain noise spectroscopy which permits to extract phase and amplitude noise Power Spectral Densities. Their analysis in the frame of theoretical models allows direct extraction of the nonlinear parameters, but also to quantify the technological relevant phase noise. This is demonstrated for magnetic tunnel junction devices. A second method is the analysis of higher harmonics linewidth, where it is shown that due to the non-isochronous property of STOs, the relationship between Dfn and Df1 is non-trivial and allows to extract NU and Gp. We then apply the information gathered on the autonomous dynamics of STOs to understand the non-autonomous dynamics of STOs that are a prerequisite for the use of STOs in complex RF architectures. It is shown experimentally how the nonlinear parameters influence this non-autonomous behaviour

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Wang, Mingchao. "Numerical investigation of graphene and graphene-polymer nanocomposites". Thesis, Queensland University of Technology, 2014. https://eprints.qut.edu.au/76082/1/Mingchao_Wang_Thesis.pdf.

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This thesis is a comprehensive and deep investigation on graphene and graphene-polymer nanocomposites. It explores the strong structure-property relationships in both graphene and graphene-based polymeric nanocomposites. A number of significant conclusions, including failure mechanism in graphene, interfacial load transfer and thermal transport mechanisms in graphene-polymer nanocomposites, have been drawn through both atomistic simulations and theoretical analysis. These results can provide direct guidelines for development of new graphene-based materials and devices.

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33

Prédélus, Dieuseul. "Rôle des hétérogénéités texturale et structurale du sol sur le transfert et la rétention des nanoparticules dans la zone non saturée : Expérimentation et modélisation". Thesis, Vaulx-en-Velin, Ecole nationale des travaux publics, 2014. http://www.theses.fr/2014ENTP0006/document.

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La production croissante des nanoparticules issues du développement des nanotechnologies et leur incorporation dans des produits de consommation vont inévitablement conduire à leur introduction dans l’environnement. Ces particules peuvent constituer un vecteur de substances polluantes en raison du transport facilité des contaminants organiques ou inorganiques potentiellement adsorbés sur leurs surfaces ou représentent elles-mêmes un risque pour l’environnement et la santé humaine. La zone non saturée joue une fonction importante de filtration naturelle des eaux de recharge des nappes. Les mécanismes de transport et de rétention des nanoparticules à travers cette zone sont complexes du fait des hétérogénéités de type structural et textural de celle-ci. Ces hétérogénéités sont à l'origine des écoulements préférentiels et d’un grand nombre de facteurs d'interaction physico-chimiques liés aux propriétés des nanoparticules et de la zone non saturée elle-même. L'objectif de la thèse est de mieux comprendre les effets de ces hétérogénéités sur le transport des nanoparticules dans un milieu non saturé hétérogène afin de mieux prévenir le devenir des nanoparticules dans le sol. Dans ce contexte, trois matériaux granulaires (un sable et des mélanges sable-gravier) ont été mis en place en colonne (10 cm de diamètre x 30 cm de hauteur) et dans le lysimètre LUGH du LEHNA (100 x 160 x 100 cm3) pour simuler le transport des nanoparticules dans le sol. Le but est de déterminer le rôle des hétérogénéités texturale (différentes granulométries) et structurale (barrière capillaire) du sol, en prenant en compte les effets de la force ionique de la solution et de la vitesse d’écoulement sur le transfert des nanoparticules en conditions non saturées. Des nanoparticules de silice marquées par des molécules organiques fluorescentes ont été développées en tant que nanotraceur particulaire dans le cadre de cette étude, l’ion bromure a été utilisé pour caractériser l’écoulement de l’eau. Le modèle de transfert de non équilibre hydrodynamique à fractionnement de l'eau en deux phases mobile et immobile, MIM, incluant un terme de rétention et de relargage des nanoparticules, décrit correctement les courbes d'élution de nanoparticules, pour les expériences en colonne. Cette étude a permis de caractériser les effets liés aux différentes tailles des grains du sol et à la barrière capillaire sur la rétention des nanoparticules. Les expériences réalisées avec différentes forces ioniques montrent que pour les forces ioniques comprises entre 1 et 50 mM, la rétention est croissante comme prédit la théorie DLVO ; cependant à partir d’une force ionique supérieure à 100 mM il se produit une inversion de la rétention. Lorsque la vitesse d’écoulement diminue, la rétention augmente, probablement en partie à l’interface air-eau. Le lysimètre LUGH a permis d’identifier le rôle de la barrière capillaire sur la rétention des nanoparticules. Un modèlenumérique 3D basé sur l’équation de Richards pour l’écoulement et les équations convection dispersion couplées avec un module de rétention pour les nanoparticules a été dévelopé. Les résultats montrent que la rétention a augmenté à l’interface sable-milieu bimodal. Le profil de rétention de nanoparticules indique qu’elles sont majoritairement retenues en surface du sol, puis la rétention diminue avec la profondeur, pour les expériences réalisées en colonne. Le nanotraceur constitue un outil puissant pour l’étude du rôle des hétérogénéités dans le transfert des particules dans un sol non saturé
Increasing production of nanoparticles from nanotechnology development and incorporation into consumer products will inevitably lead to their introduction into the environment. These particles can be a vector of pollutants due to the facilitated transport of organic and inorganic contaminants potentially adsorbed on their surfaces or represent a risk to the environment and human health themselves. The unsaturated zone plays an important function of natural water filtration recharge. The transport and retention mechanisms of nanoparticles through this zone are complex due to the structural and textural soil heterogeneities. These heterogeneities are causing preferential flows and are responsible a large number of physical and chemical interaction related to the nanoparticles properties. The aim of the thesis is to better understand effects of soil heterogeneities on the transport of nanoparticles in a heterogeneous unsaturated media to better prevent the fate of nanoparticles in the vadose zone. In this context, three granular materials (sand and sand - gravel mixtures) were introduced in column (10 cm diameter x 30 cm high) and the lysimeter LUGH of Lehna (100 x 160 x 100 cm3) to simulate the transport of nanoparticles in the soil. The goal is to determine the role of heterogeneous textural (different sizes) and structural (barrier capillary) heterogeneities of the soil, taking into account the effects of the ionic strength of the solution and the flow rate on the transfer of the nanoparticles in unsaturated conditions. Silica nanoparticles labeled with fluorescent organic molecules have been developed as particulate v in this study, the bromide ion has been used to characterize the flow of water. The transfer model of non-equilibrium hydrodynamic fractionation of water and two mobile and immobile phases, MIM, including a retention and release term of the nanoparticles, properly described breakthrough curves of nanoparticles on column experiments. This study allowed to characterize the effects related of different grain sizes of soil and capillary barrier on the nanoparticle retention. Experiments with different ionic strengths show for the ionic strength between 1 and 50 mM, the retention increased as predicted by the DLVO theory. However, from an ionic strengh greater than 100 mM an inversion retention occurs. When the flow rate decreases, retention increases, air - water interface increases and trapps probably the nanoparticles. Lysimeter LUGH allowed to identify the role of the capillary barrier on the retention of nanoparticles. A 3D numerical model based on Richards equation for flow and the convection dispersion equations coupled with a mechanical module for nanoparticle trapping was developed. Results show retention increased in the sand-bimodal interface. The retention profile indicates that nanoparticles are predominantly retained at the soil surface, then the retention decreases with depth, for the column experiments. The nanotracer is a powerful tool for studying the role of heterogeneous in the transfer of particles in an unsaturated soil

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34

LINDSTRÖM, KATARINA. "Bicomponent Fiber in Sound Absorbent Production : Investigation of using bicomponent fiber as adhesive between woven and nonwoven textile and how it affects the sound absorption". Thesis, Högskolan i Borås, Institutionen Textilhögskolan, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-18018.

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A new way of adhering woven textile to a nonwoven backing was explored, the end product in mind being a sound absorbent panel. Today a hot melt adhesive is sprayed on the nonwoven with woven decorating textile put on top before compression molding. This method results in an uneven layer of adhesive with the consequence of decorating textile detaching from the nonwoven and thereby a high number of discarded products. The report investigates the possibility of using a bicomponent fiber as the adhesive. This would guarantee an even layer of adhesive and make the manufacturing process one step shorter. A bicomponent fiber of core/sheath construction with a low melting polymer in the sheath was incorporated in the nonwoven upon fabrication. In the main bulk of the nonwoven a smaller ratio of bicomponent to normal polyester fiber was used, enough to stabilize the nonwoven. For the top layer of the nonwoven a higher ratio was chosen. As the nonwoven is then compression molded under heat together with the decorating textile, the low melting sheath of the bicomponent fiber will melt and create bonds within the nonwoven as well as to the textile. The ratio in the top layer was varied as well as the pressure in compression molding. The adhesion strength between nonwoven and decorating textile was tested, and the sound absorbing properties of the different manufactured samples were compared. The sound absorbing parameter of air flow resistance was tested and sound absorption was tested using impedance tube with transfer function method. Further, a way of testing transmission loss was developed by the manufacturing of a custom built impedance tube, which was then compared to the transfer function method. The results showed that a higher bicomponent percentage gave higher sound absorption in lower frequencies, but a lower sound absorption in higher frequencies. The thickness of the samples gave a positive effect on the sound absorption in all frequencies. The conclusion is to recommend a thicker material, and choose bicomponent according to which frequencies that should be absorbed and what adhesion strength is needed for end product.
Program: Textilteknik

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Oliveira, Elisandra Miranda de. "Transferência dos esforços cisalhantes em juntas de pavimentos rígidos". Universidade Federal de Goiás, 2008. http://repositorio.bc.ufg.br/tede/handle/tede/6783.

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Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq
The joint is part of the constructive process of the rigid pavement. In its implementation the section of concrete located below it is weakened and eventually becoming the most vulnerable of the pavement can arise where the possible diseases that may affect their strength and durability. Despite the importance that the joint has in the life of the rigid pavement it is not exploited, and therefore became the main subject of this study. This work is an experimental study of the sawed joint in rigid pavement of concrete with evaluation of the transference of shear strength through the saweds joints. The experimental program consisted of test of fourteen simple concrete plates with sawed joint, and adoption of the following variable: presence of smooth dowel of Ø 12,5mm, variation of the length of dowel (500 mm, 400 mm and 300 mm), variation of the thickness of the plates (120 mm and 160 mm), variation of the strength to the compression of the concrete (20 MPa and 30 MPa) and of the type of used concrete (conventional and autoadensável). These plates had been supported on natural and assayed rubber layers with static shipment application in one of the sides of the together one until the rupture of the plate. The results had shown that: the use of dowel in these meetings increases the efficiency in the transference of efforts; the increase in the thickness of the plate increases the resistant capacity of the together one, the efficiency in the transference of efforts and possesss minors displacements of the plate during the application of the shipment; the dowel with reduced size are efficient, but the bars of 400 mm present resulted next to the one to the bar in commercial size, 500 mm; the plates in autoadensável concrete after the fissuration practically do not present contribution of the concrete in the transference of efforts for the intertravamento of aggregates; the sawed joint depth of the together one has influence in the way of rupture of the plate and tack relation enters the bar of transference and concret.
A junta faz parte do processo construtivo do pavimento de concreto. Na sua execução a seção de concreto localizada abaixo dela fica enfraquecida e acaba se tornando o ponto mais vulnerável do pavimento onde podem surgir as possíveis patologias que venham a afetar a sua resistência e durabilidade. Apesar da importância que a junta possui na vida útil do pavimento de concreto este assunto é pouco explorado, e por isso se tornou o objeto principal deste estudo. Este trabalho é um estudo experimental das juntas serradas em pavimento rígido de concreto com avaliação da transferência de esforços cisalhantes através das juntas serradas. O programa experimental constou de ensaios de quatorze placas em concreto simples com junta serrada, e adoção das seguintes variáveis: presença de barra de transferência lisa de Ø 12,5mm, variação do comprimento das barras de transferência (500 mm, 400 mm e 300 mm), variação da espessura das placas (120 mm e 160 mm), variação da resistência característica à compressão do concreto (20 MPa e 30 MPa) e do tipo de concreto utilizado (convencional e autoadensável). Essas placas foram apoiadas sobre camadas de borracha natural e ensaiadas com aplicação de carregamento estático em um dos lados da junta até a ruptura da placa. Os resultados mostraram que: o uso de barras de transferência nessas juntas aumenta a eficiência na transferência de esforços; o aumento na espessura da placa aumenta a capacidade resistente da junta, a eficiência na transferência de esforços e possuem menores deslocamentos da placa durante a aplicação do carregamento; as barras com tamanho reduzido são eficientes, mas as barras de 400 mm apresentam resultados próximos ao da barra em tamanho comercial, 500 mm; as placas em concreto autoadensável após a fissuração praticamente não apresentam contribuição do concreto na transferência de esforços pelo intertravamento dos agregados; a profundidade da junta serrada tem influência no modo de ruptura da placa e relação de aderência entre a barra de transferência e o concreto.

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36

Pokorný, Emil. "Návrh konstrukce překládacího vozu". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-442813.

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The aim of the diploma thesis is the structural design of the field transfer trailer designed for harvesting work in agriculture. The first part of the thesis contains an overview of similar construction solutions and a summary of legislative requirements related to the device. In the next part is performed a description of the individual structural units, the design of the drive and the design of the screw conveyors. Based on the stated load conditions, the strength analysis of the large – volume hopper is processed, which is evaluated in the final part. An integral part of the thesis is also a partial drawing documentation. This diploma thesis was created in cooperation with the company ZDT Nové Veselí.

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37

Lundqvist, Maria J. "Quantum Chemical Modeling of Dye-Sensitized Titanium Dioxide : Ruthenium Polypyridyl and Perylene Dyes, TiO2 Nanoparticles, and Their Interfaces". Doctoral thesis, Uppsala universitet, Kvantkemi, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7141.

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Quantum chemical calculations have been used to model dye-sensitized nanostructured titanium dioxide systems that can be used in solar cells for solar energy to electricity conversion. Structural, electronic and spectral properties of isolated dyes and both bare and dye-sensitized TiO2 have been calculated with density functional theory, providing detailed information about both the separate parts and the dye-TiO2 interface. The connection between the geometry, the ligand field splitting and the lifetime of the triplet metal-to-ligand charge transfer (MLCT) excited state has been explored for a series of ruthenium polypyridyl dyes. Moreover, the relative energetics of MLCT and metal centered triplet excited states have been studied for a number of such systems. It was found that small alterations of the polypyridyl ligands can result in significant changes in ligand field splitting and in the energetics of the triplet states. Attachment of the dyes to the TiO2 surface is achieved via anchor and spacer groups. The influence of such groups on various properties of the dye and their ability to act as mediators of photo-induced surface electron transfer has been studied. Delocalization of the lowest unoccupied dye orbital onto the spacer and/or anchor group indicates that certain unsaturated groups can mediate electron transfer. With a combination of methods that enables efficient computations and a scheme for construction of metal oxide clusters, chemical models for bare TiO2 nanocrystals in the 1-2 nm size range have been developed. The electronic structures show well-developed band structures with essentially no electronic band gap defect states. Atomistic models of the interface between TiO2 nanocrystals and Ru(II)-bis-terpyridine dyes, the so-called N3 dye as well as perylene dyes are reported. Electronic coupling strengths, which provide estimates for the electron injection times, are extracted from the interfacial electronic structure and the lowest electronic excitations are calculated.

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38

Rakotonanahary, Georges. "Spectroscopie des transitions excitoniques dans des puits quantiques GaN/AlGaN". Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2011. http://tel.archives-ouvertes.fr/tel-00662445.

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Ce travail de thèse porte sur l'étude des propriétés optiques et électroniques des puits quantiques de GaN / AlGaN grâce à des techniques classiques de réflectivité résolue en angle et de photoluminescence, ainsi qu'avec la technique de photoluminescence résolue temporellement. Les expériences de photoluminescence en régime continu ont permis d'estimer les énergies des transitions excitoniques qui sont également accessibles en réflectivité. Ces techniques ont ainsi permis de mettre en évidence l'effet Stark dans les puits quantiques GaN / AlGaN. L'effet Stark sur les énergies de transition est cohérent avec la théorie des fonctions enveloppes. Les spectres de réflectivité permettent d'accéder à la force d'oscillateur des excitons grâce à leur modélisation par le formalisme des matrices de transfert, prenant en compte les phénomènes d'élargissement homogène et inhomogènes des transitions optiques. Enfin, les mesures de photoluminescence résolue en temps en fonction de la température, ont également permis d'extraire la force d'oscillateur qui est inversement proportionnelle au temps de recombinaison radiative. Cette étude a également permis de mettre en évidence l'effet Stark responsable de la diminution de la force d'oscillateur en fonction de l'épaisseur du puits quantique mais aussi en fonction de la composition d'aluminium. L'augmentation de l'épaisseur du puits entraîne une diminution du recouvrement des fonctions d'onde, et une augmentation de la composition d'aluminium intensifie le champ électrique et diminue également le recouvrement des fonctions d'onde.

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39

Warner, Wyatt Young. "Characterization of Local Void Content in Carbon Fiber Reinforced Plastic Parts Utilizing Observation of In Situ Fluorescent Dye Within Epoxy". BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/7772.

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Experimentation exploring the movement of voids within carbon fiber reinforced plastics was performed using fluorescent dye infused into the laminates observed through a transparent mold under ultraviolet light. In situ photography was used as an inspection method for void content during Resin Transfer Molding for these laminates. This in situ inspection method for determining the void content of composite laminates was compared to more common ex-situ quality inspection methods i.e. ultrasonic inspection and cross-section microscopy. Results for localized and total void count in each of these methods were directly compared to test samples and linear correlations between the three test methods were sought. Test coupons were then cut from these laminates and were used to calculate the interlaminar shear strength at certain locations throughout the laminates. Although this research did not adequately observe correlations between results obtained from ultrasonic C-scans, cross-sectional microscopy and in situ photography of the surface, it was seen that the fluid dynamics of the thermosetting epoxy used in this experimentation correlated to results obtained from previous experimentation performed by students at Brigham Young University using vegetable oil as a substitute for resin.

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40

Bednařík, Josef. "Návrh a realizace bezdrátového nabíjení pro vestavěné systémy". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-417755.

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This thesis deals with the design and realization of wireless power charging circuit for embedded systems. The research section focuses on the various ways and technologies used in applications of wireless power transfer. The theoretical part also briefly characterizes resonant inductive coupling and critical parameters of the transfer. This is followed by realization of various variants of transfer coils and electromagnetic oscillators. Wireless power charging prototype system is created and used for testing purposes to find optimal configuration of resonator. The hardware unit presented in the final part of the thesis exploits microcontroller and implemented software is extended by foreign object detection algorithm along with method to monitor battery charging state.

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41

Maluk, Cristian. "Development and application of a novel test method for studying the fire behaviour of CFRP prestressed concrete structural elements". Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/15926.

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A novel type of precast, prestressed concrete structural element is being implemented in load-bearing systems in buildings. These structural elements combine the use of high-performance, self-consolidating concrete (HPSCC) and non-corroding carbon fibre reinforced polymer (CFRP) prestressing tendons; this produces highly optimized, slender structural elements with excellent serviceability and (presumed) extended service lives. More widely, the use of new construction techniques, innovative materials, and ground-breaking designs is increasingly commonplace in today's rapidly evolving building construction industry. However, the performance of these and other structural elements in fire is in general not well known and must be understood before these can be used with confidence in load-bearing applications where structural fire resistance is a concern. Structural fire testing has traditionally relied on the use of the standard fire resistance test (i.e. furnace test) for assuring regulatory compliance of structural elements and assemblies, and in many cases also for developing the scientific understanding of structural response to fire. Conceived in the early 1900s and fundamentally unchanged since then, the standard testing procedure is characterized by its high cost and low repeatability. A novel test method, the Heat-Transfer Rate Inducing System (H-TRIS), resulting from a mental shift associated with controlling the thermal exposure not by temperature (e.g. temperature measured by thermocouples) but rather by the time-history of incident heat flux, was conceived, developed, and validated within the scope of the work presented in this thesis. H-TRIS allows for experimental studies to be carried out with high repeatability, imposing rationally quantifiable thermal exposure, all at low economic and temporal cost. The research presented in this thesis fundamentally seeks to examine and understand the behaviour of CFRP prestressed HPSCC structural elements in fire, with emphasis placed on undesired 'premature' failure mechanisms linked to the occurrence of heat-induced concrete spalling and/or loss of bond between the pretensioned CFRP tendons and the concrete. Results from fire resistance tests presented herein show that, although compliant with testing standards, temperature distributions inside furnaces (5 to 10% deviation) appear to influence the occurrence of heat-induced concrete spalling for specimens tested simultaneously during a single test; fair comparison of test results is therefore questionable if thermal exposure variability is not explicitly considered. In line with the aims of the research presented in this thesis, H-TRIS is used to carry out multiple comprehensive studies on the occurrence of concrete spalling and bond behaviour of CFRP tendons; imposing a quantified, reproducible and rational thermal exposure. Test results led to the conclusion that a "one size fits all" approach for mitigating the risk of heat-induced concrete spalling (e.g. prescribed dose of polypropylene (PP) fibres included in fresh concrete), appears to be ineffective and inappropriate in some of the conditions examined. This work demonstrates that PP fibre cross section and individual fibre length can have an influence on the risk of spalling for the HPSCC mixes tested herein. The testing presented herein has convincingly shown, for the first time using multiple repeated tests under tightly controlled thermal and mechanical conditions, that spalling depends not only on the thermal gradients in concrete during heating but also on the size and restraint conditions of the tested specimen. Furthermore, observations from large scale standard fire resistance tests showed that loss of bond strength of pretensioned CFRP tendons occurred at a 'critical' temperature of the tendons in the heated region, irrespective of the temperature of the tendons at the prestress transfer length, in unheated overhangs. This contradicts conventional wisdom for the structural fire safety design of concrete elements pretensioned with CFRP, in which a minimum unheated overhang is generally prescribed. Overall, the research studies presented in this thesis showed that a rational and practical understanding of the behaviour of CFRP prestressed HPSCC structural elements during real fires is unlikely to be achieved only by performing additional standard fire resistance tests. Hence, H-TRIS presents an opportunity to help promote an industry-wide move away from the contemporary pass/fail and costly furnace testing environment. Recommendations for further research to achieve the above goal are provided.

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42

Bouba, Oumarou. "Théories quantique et semi-classique des intégrales radiales de transitions dipolaires et multipolaires des états excités : Applications au calcul des forces d'oscillateur et des probabilités de transition dans l'approximation à une configuration". Orléans, 1986. http://www.theses.fr/1986ORLE0010.

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Calcul des intégrales radiales à l'approximation quasi classique (JWKB) des fonctions d'onde radiales, complétée par une description en termes de trajectoires elliptiques de l'électron optique. Obtention d'expressions analytiques de ces intégrales dont on simplifie le calcul à l'aide d'une méthode basée sur le développement limite d'une fonction bien adaptée à des calculs par interpolation ou extrapolation : elles s'expriment toutes en termes de deux fonctions fondamentales qui ne dépendent que de la différence entre deux nombres quantiques principaux effectifs des états initial et final. Déduction de forces d'oscillateur et probabilités de transition aussi précises que celles obtenues par quantique.

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43

Hamaïdia, Abderrahmane. "Etude par dichroisme circulaire magnetique et par resonance paramagnetique electronique des centres colores dans caf : :(2) et srf::(2) dopes par des ions alcalins". Caen, 1987. http://www.theses.fr/1987CAEN2027.

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Etude des centres colores de quatre cristaux de fluorures alcalinoterreux dopes par li, na et k, colores additivement ou par rayonnement gamma. Mise en evidence de deux types de centre f::(a) par dichroisme circulaire magnetique. On a etudie ensuite le centre f::(2a) dont il a ete montre que l'analogie avec le centre f::(2) est trompeuse. D'autres centres ont ete etudies. On a pu comprimer l'identification de l'un d'entre eux comme f::(3a) ionise

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44

Gongassian, Michel. "Etude theorique du rayonnement emis par un plasma d'hexafluorure de soufre". Toulouse 3, 1986. http://www.theses.fr/1986TOU30066.

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Calcul des coefficients d'absorption et d'emission du rayonnement dans un plasma de sf6 pour des temperatures de 5 000 a 30 000k et une pression de 1 a 8 atm. Les especes considerees sont les electrons, les atomes neutres f et s,les ions negatifs f**(-) et s**(-) et les ions atomiques positifs une et deux fois charges. Le rayonnement total tient compte des raies, de la recombinaison radiative, de l'attachement electronique et du bremsstrahlung (electron-ion et electron-atome)

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45

Fatemi, Fataneh. "Etude de la dynamique des domaines de la NADPH-cytochrome P450 réductase humaine". Thesis, Paris 11, 2013. http://www.theses.fr/2013PA114821.

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La NADPH cytochrome P450 réductase (CPR) est une flavoprotéine multidomaines appartenant à la famille des diflavines réductases et un des composants essentiels du système redox des cytochromes P450. La CPR est formée de deux domaines catalytiques contenant des groupements prosthétiques FAD et FMN et d'un domaine de connexion. Le domaine FAD reçoit deux électrons du NADPH et les transfère un par un au domaine FMN, qui, à son tour, les transfère aux accepteurs. Le transfert d’électron du FMN vers les accepteurs nécessite un déplacement du domaine FMN par rapport au reste de la molécule. Au fils des années, les études structurales menées sur la CPR ont mis en évidence la réorganisation structurale et l’arrangement des domaines dans cette protéine. Cependant, les résultats de ces analyses ne fournissent pas d’informations concernant la vitesse à laquelle les mouvements des domaines de la CPR s’effectuent et n’incluent toujours pas les paramètres qui induisent le changement conformationnel ainsi que l'influence de ces changements sur l’activité catalytique de la CPR.Le projet de cette thèse a consisté à apporter de nouveaux éléments de compréhension sur la relation entre les changements conformationnels de la CPR et son cycle catalytique. La première partie de ce travail a porté sur le développement de stratégies de préparation au marquage des domaines catalytiques de la CPR, destinés à l’étude dynamique de cette protéine par le FRET. Différentes stratégies ont été envisagées parmi lesquelles l’incorporation de p-acétyle phénylalanine sur des positions définies dans la CPR. La deuxième partie de ce travail est consacrée à l’étude dynamique de la CPR via des techniques de RMN et SAXS combinées à des approches biochimiques. Les expériences menées ont permis de caractériser en solution et en absence de NaCl, la présence d’un état rigide, globulaire en conformation fermée dans laquelle les domaines FMN et FAD sont maintenus « verrouillés » par des interactions à l’interface entre ces deux domaines. L’augmentation de la concentration en NaCl permet une transition de cet état « verrouillé » vers un état plus ouvert pour lequel il n’y a plus d’interface entre les domaines FAD et FMN. L’état « déverrouillé » de la CPR correspond à un équilibre dynamique entre un ensemble de conformations en échange rapide. Cet équilibre est contrôlé par la force ionique et l’activité catalytique de la CPR est maximale lorsque les états verrouillés et déverrouillés sont également peuplés. Le modèle cinétique proposé par nos études a permis de mettre en évidence un lien direct entre la dynamique des domaines et l’activité du transfert d’électron au cours de cycle catalytique de la CPR
NADPH cytochrome P450 reductase (CPR) is a multidomain flavoprotein that belongs to the diflavines reductase family. It is an essential component of redox system delivering electrons for cytochrome P450. CPR is composed of two catalytic domains containing FAD and FMN prosthetic groups and a connecting domain. FAD domain receives two electrons from NADPH and transfers them one by one to the FMN domain, which in turn transfers them to the acceptor. The electron transfer from FMN to the acceptor requires a large domain movement. Over the years, structural studies of CPR have highlighted the reorganization and arrangement of domains in this protein. However, the results of these analyses do not provide any information about how fast the domains movements takes place in CPR, and do not always include the parameters that induce conformational change as well as influence of those changes on the catalytic activity of the CPR. This thesis aims to bring new elements of comprehension on the relationship between conformational changes in CPR and its catalytic cycle. The first part of the work concerned the development of strategies to label the catalytic domains of CPR, a prerequisite for the dynamic study of this protein by FRET. Different strategies have been proposed including the incorporation of p-acetyl phenylalanine at defined positions in CPR. The second part of this work is devoted to the dynamic study of CPR through a combined SAXS, NMR and biochemical approaches. The experiments conducted allowed to characterize the presence of a rigid and globular state of closed conformation for CPR, in solution and in the absence of NaCl. In this conformation the FMN and FAD domains are kept "locked" by interface interactions between these two domains. Increasing the NaCl concentration permits the transition from the "locked" stats to an open conformation in which there is no more interface between the FAD and FMN domains. The "unlocked" state of CPR is a dynamic equilibrium between ensembles of conformations in fast exchange. This equilibrium is controlled by the ionic strength and CPR presents its maximum catalytic activity when the locked and unlocked states are equally populated. We proposed a kinetic model which allows demonstrating a direct link between the domain movement and electron transfer activity during the catalytic cycle of CPR

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Bui, Dang Thanh. "Étude et réalisation d'un système instrumental de stabilisation d'un modulateur électrooptique : application à l'amélioration du comportement d'un oscillateur optoélectronique". Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2011. http://tel.archives-ouvertes.fr/tel-00618230.

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Les modulateurs electro-optiques (EOM) sont des composants importants dans les systemes de telecommunication. Malheureusement, ils ne sont pas parfaitement stables dans Ie temps et leur fonction de transfert (TF) a tendance a se decaler durant Ie temps d'operation. La derive de la TF d'un EOM peut etre expliquee par des effets differents tels que les changements de la temperature ambiante, de la polarisation ou de l'efficacite de couplage optique. La these presente une methode de me sure de la derive de la TF de I'EOM (a grace d'estimation du comportement non-linearite du modulateur, NLl), et propose deux systemes instrumentaux pour ameliorer son fonctionnement: Ie premier pour contraler la temperature de l'EOM, il est possible de forcement reduire cette derive, Ie deuxieme pour compenser la derive (la stabilisation du point de fonctionnement autour du point quadrature est obtenue jusqu'au 0,22% ou la fluctuation de phase est de 0,44°). Ces techniques ont ete aussi appliquees pour ameliorer Ie comportement d'un oscillateur optoelectronique haute frequence. Nous avons realise les experiences par asservissement de temperature, par compensation de la derive. Pour une stabilite de I'OEO a court terme, la stabilisation de la frequence est amelioree jusqu'a 28% en utilisant un contrale de temperature seule etjusqu'a 71 % avec les deux processus. Pour une stabilite de l'OEO a long terme, en deux cas sans contra Ie, I'OEO fonctionne pendant 3 heures et pendant 1,6 heure (puis I'OEO ne marche plus). En utilisant une compensation de la derive de la TF de I'EOM, l'OEO fonctionne bien meme apres 7 heures et 8 heures.

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TSIMBROVSKA, MARIANA. "Dégradation des bétons à hautes performances soumis à des températures élevées : évolution de la perméabilité en liaison avec la microstructure". Université Joseph Fourier (Grenoble), 1998. http://www.theses.fr/1998GRE10030.

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Les betons a hautes performances (bhp), grace a leur durabilite et resistance mecanique elevees, sont de plus en plus utilises dans la construction. Cependant, sous certaines sollicitations thermiques (incendie, accident nucleaire) ces betons manifestent parfois un comportement fragile appele eclatement. Un des principaux parametres regissant l'eclatement est la permeabilite qui controle les transferts des fluides. Cette propriete est fonction de la microstructure du materiau, caracterisee par la porosite, la distribution des tailles de pores, la connectivite et la tortuosite du reseau poreux, la densite et l'ouverture des fissures. Ce travail a pour but d'etudier l'evolution de la permeabilite intrinseque des bhp degrades suite a un echauffement (jusqu'a 400c) et de correler cette evolution aux caracteristiques de microstructure. Une etude comparative avec les betons ordinaires est effectuee. La permeabilite intrinseque des betons est estimee a partir des mesures de la permeabilite aux gaz. Avant traitement thermique la permeabilite intrinseque des bhp est inferieure d'environ un ordre de grandeur a celle des betons ordinaires. Cependant sous l'effet de la temperature cette propriete augmente plus rapidement dans les bhp (2 ordres de grandeur) et apres traitement thermique a 400c les bhp sont plus permeables que les betons ordinaires. Le sous-espace poreux efficace vis-a-vis de la permeabilite est identifie comme celui constitue de pores de diametre superieur a 0,1m. L'evolution de ce sous-espace poreux avec la temperature et la microfissuration expliquent les variations de la permeabilite dans chaque type de materiau. Trois modeles reliant la permeabilite a la microstructure sont appliques et leurs previsions sont comparees aux resultats experimentaux. Cette comparaison est satisfaisante mais montre les limites des representations topographique et geometrique des reseaux poreux utilisees dans la modelisation des transferts de masse.

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Nitsche, Robert. "Optical Properties of Organic Semiconductors: from Submonolayers to Crystalline Films". Doctoral thesis, [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=979835186.

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Nitsche, Robert. "Optical Properties of Organic Semiconductors: from Submonolayers to Crystalline Films". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2006. http://nbn-resolving.de/urn:nbn:de:swb:14-1147356837431-39487.

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We have measured the optical properties of films of the organic semiconductors PTCDA (3,4:9,10-perylene-tetracarboxylic dianhydride) and HBC (peri-hexabenzocoronene), prepared by Organic Molecular Beam Expitaxy (OMBE), on different substrates by means of Differential Reflectance Spectroscopy (DRS). The optical setup enables us to directly follow the thickness dependent optical properties of the organic films, starting from submonolayer coverage up to thicker films on the order of 20 monolayers (ML) film thickness. Due to the different optical nature of the different substrates used, i.e., mica, glass, Au(111), and HOPG, the direct interpretation of the DRS signal is not feasible. Therefore, we have proposed a method by which the calculation of the optical constants n (index of refraction) and k (absorption index) of thin films on arbitrary substrates from just one spectral measurement (in our case the DRS) becomes possible. The results fulfill a priori a Kramers-Kronig consistency and no specific model is needed to express the spectral behavior of the optical constants. Based on our method, we have successfully calculated the optical constants, and therefore the absorption behavior, of films of different thickness of PTCDA on mica, glass, Au(111), and HOPG, as well as of HBC on mica, glass, and HOPG. Extrinsic effects due to island growth or the presence of a polarizable substrate (screening) have been accounted for. We have introduced a finite dipole model which considers the extended geometry and anisotropy of the organic molecules. The calculated absorption behavior is discussed in great detail in terms of spectral changes with varying film thickness, different growth modes, degree of ordering of the films, interactions with the substrates and oscillator strength. A direct observation of a monomer-dimer transition in solid films could be observed for the first time. Our results indicate an exciton delocalization over about 4 molecules for both molecules.

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Benferhat, Ramdane. "Realisation d'un ellipsometre spectroscopique a modulation de phase fonctionnant dans l'infrarouge : application a l'etude des proprietes vibrationnelles de couches ultraminces organiques ou semiconductrices amorphes". Paris 6, 1987. http://www.theses.fr/1987PA066259.

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Mise au point et realisation de l'appareil, dont le fonctionnement est base sur l'utilisation combinee d'un modulateur photoelastique et d'un traitement numerique rapide du signal; description detaillee du systeme optique et electronique. Application a l'etude des proprietes vibrationnelles de couches ultraminces des deux types : echantillons constitues de 1,3,9,19 monocouches organiques langmuir-blodgett et couches a-si:h de 50 a 500 a d'epaisseur, deposees sur verre. Mise en evidence de l'influence du substrat sur le mecanisme de depot et analyse de l'orientation des chaines aliphatiques dans le premier cas; dans le deuxieme cas l'etude montre que le materiau obtrenu au debut du depot est nettement different de celui des echantillons epais; identification des vibrations de valence des liaisons sim et sih::(2) sur couches de 5 a, effet de l'introduction du carbone dans a-si:h

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